(1) Field of the Invention
The present invention relates to an image processing apparatus containing at least one bus, a central processing unit and a plurality of units each may request use of one of the bus or a data transfer among the plurality of units using the bus. The present invention relates, in particular, to a facsimile terminal apparatus wherein image data written or printed on paper is read, encoded, and transmitted, and image data transmitted to the facsimile terminal apparatus is received, decoded, and output through a printer.
(2) Description of the Related Art
Since transfer operations of a large amount of image data must be carried out in an image processing apparatus as above, DMA (Direct Memory Access) transfer operations are utilized in the image processing apparatus, whereby a CPU (Central Processing Unit) is not required to directly control the transfer operations of the image data.
FIG. 1 is a block diagram illustrating a conventional construction of a facsimile terminal apparatus. In FIG. 1, reference numeral 1' denotes a CPU, 6' denotes a memory, 8 denotes a DMA controller, 11' denotes a ROM (Read Only Memory) for storing firmware for the operation of the CPU 1', 20' denotes a bus, 21' denotes an address bus in the bus 20', 22' denotes a control signal bus in the bus 20', 23' denotes a data bus in the bus 20', a1 denotes control signal lines for transmitting data transfer request signals, b1 denotes control signal lines for transmitting bus acknowledge signals, c1 denotes control signal lines for transmitting a bus-request-to-CPU signal, d1 denotes control signal lines for transmitting a bus-acknowledge-from-CPU signal, 51 denotes a read-in image input unit, 52 denotes an image output unit, 53 denotes a compression/expansion unit, 54 denotes a communication control unit, and 55 denotes a MODEM